Field of the Invention
The present invention relates to irrigation nozzles adapted for use with fluidic circuits.
Discussion of the Prior Art
Irrigation systems employ sprinkler nozzles to generate sprays of desired patterns, for use in areas having specific geometries. For example, if a rectangular area is to be irrigated, a sprinkler or irrigation nozzle adapted for generating a rectangular spray is called for. Rectangular spray nozzles therefore comprise a major category of specialty sprays in irrigation, and they are distinguished from regular sprays, which usually provide circle or arc spray pattern.
For purposes of nomenclature, LCS (Left corner strip) 110, illustrated in FIG. 1A, is a common term to describe the location and function of a specialty LCS rectangular spray nozzle 100. Similarly, RCS (Right corner strip) 120 illustrated in FIG. 1B is the common term to describe the location and function of a specialty RCS rectangular spray nozzle 102, and SST (Side strip) 130 illustrated in FIG. 1C is the common term to describe the location and function of a specialty SST rectangular spray nozzle 104.
Typically, a rectangular spray nozzle is much more difficult to design compared with the regular arc spray nozzle, because of the high gradient of throw change around the diagonal line, especially for a high aspect ratio (length/width) shape with a low PR (precipitation rate). FIGS. 2 and 3 illustrate theoretical ideal throw patterns for an irrigation area defining a 4 ft×15 ft RCS and a 4 ft×9 ft RCS spray, especially if overspray and waste are to be minimized. Since water is now an increasingly valuable commodity, overspray (outside the intended area) and waste are becoming intolerable.
For those situations where overspray beyond a desired rectangular irrigation area does not matter, fluidic oscillators can be used to generate a very uniform spray pattern. For example, commonly owned U.S. patent application Ser. No. 10/968,749 discloses a fluidic oscillator insert 18 suitable for use in spraying cleaning fluid onto a windshield and utilizes a pressurized liquid to generate a uniform spatial distribution of droplets; this fluidic oscillator has (a) an inlet for the pressurized liquid, (b) a set of three power nozzles that are fed by the pressurized liquid, (c) an interaction chamber attached to the nozzles and which receives the flow from the nozzles, where this chamber has an upstream and a downstream portion, with the upstream portion having a pair of boundary edges and a longitudinal centerline that is approximately equally spaced between the edges, and where one of the power nozzles is directed along the chamber's longitudinal centerline. Fluidic insert 18 also defines a throat from which the liquid exhausts or sprays from the interaction chamber and defines an island in the interaction chamber, where the island is situated downstream of the power nozzle that is directed along the chamber's longitudinal centerline. In the illustrated fluidic insert 18, the oscillator is further configured such that: (i) one of the power nozzles is located proximate each of the chamber's boundary edges, (ii) its nozzles are configured to accelerate the movement of the liquid that flows through the nozzles, (iii) its throat has right and left sidewalls that diverge downstream, and (iv) the power nozzles and island are oriented and scaled such as to generate flow vortices behind the island that are swept out of the throat in a manner such that these vortices flow alternately proximate the throat's right sidewall and then its left sidewall. And the fluidic oscillator with insert 18 will generate a uniform spray of droplets, but that spray is not readily adapted to spray onto a defined irrigation area with a selected shape such as a rectangle.
The present invention seeks to solve these difficulties and permit irrigation of rectangular zones with a PR (precipitation rate)≦1 inch/hour. Currently there is no fixed head nozzle in the market with such a low PR. Most current irrigation sprinklers use either a rotor or fixed heads to create a rectangular spray pattern. A rotor head sprinkler is capable of throwing long distance jet with low PR (typically 0.5 inch/hour for 4 ft×15 ft specialty spray). But since the rotor head is gear driven by flowing water, its life time is low due to the gear/shaft wear or clogging. Moreover, the gear set assembly is costly and bulky. By way of contrast, a conventional fixed head sprinkler is low in cost but has to work with a high PR (typically 2 inch/hour for 4 ft×15 ft LCS/RCS) for a full coverage.
A low PR is preferred for most of the irrigation applications. With low PR, water will be allowed to soak into the ground slowly instead of running off from soil surface. Another advantage of low PR is that with the specified pressure and flow rate supply low PR sprinklers are able to cover more area.
There is a need, therefore, for an inexpensive, durable and efficient irrigation nozzle and method for generating specialized rectangular spray patterns.